I acquired two pairs of C53 Libra cabinets. One pair is loaded with a hodgepodge of LE14C, LX2-1/LX2 crossovers plus LE175DHL and N1200 crossovers. Go figure. The other pair of cabinets is more standard with LE14A + LE175DHL + LX10 crossovers. Each cabinet has a 4" port or hole in the front baffle. But the pair with the extra components also has a tuning tube running back from it.

I intend to keep the 2nd pair, essentially the S1 system in C53 Libras, but wish further information on the port and tube? Which is correct?